Knowledge concerning the biological actions of keratinocyte growth factor (KGF) and hepatocyte growth factor/scatter factor (HGF/SF) and the structure-function relationships that govern interactions with their respective receptors has been greatly extended. KGF and HGF/SF are both produced by human adult lung fibroblasts and stimulate the proliferation of alveolar type II cells in vitro. Either or both factors therefore may have an important role in the homeostatic maintenance of alveolar tissue architecture or its restoration following injury. KGF expression is dramatically induced in the endometrium of the Rhesus monkey by progesterone. In situ hybridization revealed KGF transcript to be most abundant in the stromal cells and smooth muscle cells of the spiral arteries in the basal region of the endometrium. This KGF induction also was documented at the protein level by analyzing whole tissue extracts with a two-site ELISA and RIA. In another context, it was demonstrated that KGF promotes keratinocyte migration and production of urokinase activity, consistent with its proposed role in wound healing and tissue remodeling. Using a synthetic peptide derived from a portion of the KGF receptor amino acid sequence, part of the KGF binding site was identified and it was determined that this peptide is an antagonist of KGF biological activity. A naturally occurring, truncated form of HGF/SF extending only through the first kringle domain was expressed recombinantly and demonstrated to interact with c-Met, the HGF/SF receptor. This is the smallest form of HGF/SF shown to have an effect on the c-Met protein.